Selective bilateral hippocampal volume loss in chronic schizophrenia

Background: The hippocampus is implicated in the pathophysiology of schizop hrenia; however, volumetric changes are subtle and have limited diagnostic specificity. It is possible that the shape of the hippocampus may be more c haracteristic of schizophrenia. Methods: Forty-five patients with chronic schizophrenia and 139 healthy, co ntrol subjects were scanned using magnetic resonance imaging. Hippocampi we re traced manually, and two-dimensional shape information was analyzed. Results: Two shape factors were found to be adequate to represent variance in the shape of the hippocampus. One of these factors, representing volume loss behind the head of the hippocampus, provided a degree of discriminatio n between patients with chronic schizophrenia and healthy control subjects; however, overall hippocampal volume following appropriate adjustment for b rain volume showed a similar level of discrimination. Patients with chronic schizophrenia were best characterized using these two measures together, b ut diagnostic specificity was only moderate. Conclusions: This study identified that less of the hippocampus was distrib uted in its posterior two-thirds in patients with chronic schizophrenia, an d specifically in the region just posterior to the hippocampal head. Group discrimination on the basis of hippocampal volume and shape measures was mo derately good. A full three-dimensional analysis of hippocampal shape, base d on large samples, would be a useful extension of the study. Biot Psychiat ry 2001;50:531-539 (C) 2001 Society of Biological Psychiatry.